@ChristianAdams: Many thanks for your detailed responses here, they are most useful. One major contradiction though is confusing me:

• You state in the first line of your answer that the answer is about instigating Network Links for Google Earth WEB i.e. 'Loading a KML or KMZ file via NetworkLink in Google Earth for web . . .' but then at the end of your comments here say 'Unfortunately Earth web does not yet support NetworkLinks in cloud projects, . . .'!! I have been struggling to implement any Network Link for a Project in Google Earth Web. Please could you clear up the confusion I have alluded to? Many Thanks.